Conventionally, molding materials including acryl syrup have been used in a variety of fields. For example, Japanese Examined Patent Application No. 11652/1989 (Tokukosho 64-11652) discloses crosslinkable acryl syrup including a polymer having a carboxyl group, and a crosslinkable monomer having a plurality of functional groups. Japanese Examined Patent Application No. 24357/1986 (Tokukosho 61-24357) discloses acryl syrup having a carboxyl group. Further, Japanese Examined Patent Application No. 2189/1978 (Tokukosho 53-2189) discloses syrup obtained by processing a thiol compound remaining in the syrup using maleic anhydride and a basic compound.
The thiol compound is typically used as a chain transfer agent for use in the polymerization reaction, and a stabilizer of the syrup. Therefore, the syrup obtained by a polymerization reaction in a presence of thiol compound contains unreacted thiol compound. Such residual thiol compound in the syrup may cause odor to be generated. The residual thiol compound also causes the viscosity to be gradually increased on storage, and may cause the syrup to be gelled. Furthermore, molded articles prepared from the molding materials including syrup are inferior in their solvent-resistance, water-resistance, and weathering resistance.
The described conventional acryl syrup is inferior in its storage stability (a so-called shelf life) as molding materials. Besides, a long time is required for curing such molding materials including acryl syrup, and the molded article prepared from the molding materials is inferior in its heat-resistance and solvent-resistance. On the other hand, when adopting the acryl syrup having no carboxyl group, a long time is required for manufacturing acryl syrup. The described deficiencies of the conventional acryl syrup have led to the need for development of a desirable (meth)acryl syrup and a manufacturing method of the same, and molding materials including the same.
Additionally, the method disclosed in Japanese Examined Patent Application No. 2189/1978 (Tokukosho 53-2189) is only applicable to the specific syrup. Thus, the method does not offer the solution of eliminating the described problems associated with the conventional (meth)acryl syrup.
The present invention is achieved in the hope of finding the solution to the above-mentioned problems. Accordingly, the first object of the present invention is to provide (meth)acryl syrup which shows an excellent storage stability as a molding material. The second object is to provide a manufacturing method of the (meth)acryl syrup which permits (meth)acryl syrup to be manufactured in a shorter time compared with the conventional method. The third object of the present invention is to provide molding materials which can be cured in shorter period of time compared with the conventional method, while having excellent properties in their heat-resistance, solvent-resistance, weathering resistance and water-resistance, etc.